In diagnosing and treating certain medical conditions, it is often desirable to perform a biopsy, in which a specimen or sample of tissue is removed for pathological examination, tests and analysis. A biopsy typically results in a biopsy cavity occupying the space formerly occupied by the tissue that was removed. As is known, obtaining a tissue sample by biopsy and the subsequent examination are typically employed in the diagnosis of cancers and other malignant tumors, or to confirm that a suspected lesion or tumor is not malignant. Treatment of cancers identified by biopsy may include subsequent removal of tissue surrounding the biopsy site, leaving an enlarged cavity in the patient's body. Cancerous tissue is often treated by application of radiation, by chemotherapy, or by thermal treatment (e.g., local heating, cryogenic therapy, and other treatments to heat, cool, or freeze tissue).
Cancer treatment may be directed to a natural cavity, or to a cavity in a patient's body from which tissue has been removed, typically following removal of cancerous tissue during a biopsy or surgical procedure. For example, U.S. Pat. No. 6,923,754 to Lubock and U.S. patent application Ser. No. 10/849,410 to Lubock, the disclosures of which are all hereby incorporated by reference in their entireties, describe devices for implantation into a cavity resulting from the removal of cancerous tissue which can be used to deliver cancer treatments to surrounding tissue. One form of radiation treatment used to treat cancer near a body cavity remaining following removal of tissue is “brachytherapy” in which a source of radiation is placed near to the site to be treated.
Lubock above describes implantable devices for treating tissue surrounding a cavity left by surgical removal of cancerous or other tissue that includes an inflatable balloon constructed for placement in the cavity. Such devices may be used to apply one or more of radiation therapy, chemotherapy, and thermal therapy to the tissue surrounding the cavity from which the tissue was removed. The delivery lumen of the device may receive a solid or a liquid radiation source. Radiation treatment is applied to tissue adjacent the balloon of the device by placing radioactive material such as radioactive “seeds” in a delivery lumen. Such treatments may be repeated if desired.
A radiation source such as a miniature or micro-miniature x-ray tube may also be used (e.g. U.S. Pat. No. 6,319,188). The x-ray tubes are small, flexible and are believed to be maneuverable enough to reach the desired treatment location within a patient's body. The radiation source is to be removed following each treatment session, or remains in place as long as the balloon remains within the body cavity. Other inflatable treatment delivery devices and systems may be used to treat cancer in tissue adjacent a body cavity.
When performing an image guided biopsy procedure an obturator is used as a place holder and is located in tissue so that its distal tip will be located at the point in the patient's body where the biopsy is to be taken or where a biopsy site marker or tissue marker is to be placed after a biopsy procedure. Subsequent images are acquired that can confirm the correct placement of the obturator. When the obturator is placed at the desired location within the body, blood can enter the lumen of the obturator prior to delivery of the tissue markers. This backflow of blood into the obturator creates a risk of blood clotting.
Current obturators are constructed of homogeneous materials. During magnetic resonance imaging (MRI) guided biopsies, the tip of the obturator is located by indexing through many cross sectional views (typically every 2 mm, but higher and lower discriminations are possible). The material of the obturator will be distinguishable in the cross sectional images to a varying degree depending on the morphology of the tissue and the obturator's own material makeup. Since the prior obturators were homogeneous, the signature of the obturators will not vary from one cross-sectional image to the next along its length. The tip of the obturator is located by selecting the first cross-sectional image in which the obturator is not seen. This result can be visually ambiguous depending on the relative strength of the image signature of the obturator compared to the surrounding tissue.